This test may be useful in discriminating among the various vasculitides. Cytoplasmic (c-ANCA) antibodies giving diffuse cytoplasmic staining are directed against Proteinase-3, and are suggestive of a spectrum of diseases which includes Wegener's Granulomatosis, polyarteritis nodosa, Churg-Strauss syndrome, and primary necrotizing and crescentic glomerulonephritis. Perinuclear (p-ANCA) staining is due to antibodies to myeloperoxidase (MPO) and other antigens such as elastase and lactoferrin, and is less specific.